Loss of pollen-specific phospholipase NOT LIKE DAD triggers gynogenesis in maize

Gynogenesis is an asexual mode of reproduction common to animals and plants, in which stimuli from the sperm cell trigger the development of the unfertilized egg cell into a haploid embryo. Fine mapping restricted a major maize QTL (quantitative trait locus) responsible for the aptitude of inducer lines to trigger gynogenesis to a zone containing a single gene NOT LIKE DAD (NLD) coding for a patatin-like phospholipase A. In all surveyed inducer lines, NLD carries a 4-bp insertion leading to a predicted truncated protein. This frameshift mutation is responsible for haploid induction because complementation with wild-type NLD abolishes the haploid induction capacity. Activity of the NLD promoter is restricted to mature pollen and pollen tube. The translational NLD::citrine fusion protein likely localizes to the sperm cell plasma membrane. In Arabidopsis roots, the truncated protein is no longer localized to the plasma membrane, contrary to the wild-type NLD protein. In conclusion, an intact pollen-specific phospholipase is required for successful sexual reproduction and its targeted disruption may allow establishing powerful haploid breeding tools in numerous crops.     

Use of flow cytometry to detect genotoxins by the Salmonella sulA-test

The Salmonella sulA-test using Salmonella typhimurium TA1538/pEM1968 ( sulA:: lacZ) is a new SOS-repair inducing system that detects mutagens and carcinogens. The b-galactosidase activity, currently detected by colorimetric dosage, can be measured by flow cytometry using a fluorescent substrate (fluorescein-di-b-D-galactopyranoside). Comparison of the dose-response relationships of eight chemicals determined by the two techniques showed that the Salmonella sulA-test combined with the flow cytometry technique was accurate and reliable as it covered a large number of cells in a short time.